An interesting take on the modest curve that TWD throws into the traditional zombie universe: the entire population is already infected at the start of the zombie infestation. Everyone is going to turn no matter how they die. (Unless the brain is destroyed, the prosthetics/makeup department insisted on that).

It presents a conundrum: if you're already infected, why would an otherwise non-fatal bite from a zombie suddenly cause you to turn? The short answer: the mouths of rotting corpses are full of some really nasty bacteria, and their bite is more akin to an injection of venom than it is a viral infection.